Modification of keratins with sulphones and related compounds



States of America 'as represented bythe Secretary of Agriculture 7 NoDrawing. Filed Oct. 15, 1956, Ser. No. 616,112

' s Claims. (01. 8-128) (Granted under Title 35, U.S. Code (1952), see.266) A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government with the power to grant sublicenses for such purposes,is hereby granted to the Government of the United States of America.

This invention relates to the chemical modification ofkeratinrnaterials, particularly wool in the form of fibers, threads,yarns, fabrics, or wool waste. The invention is also applicable to othertypes of keratinous materials, as for example, various types ofanimalhair such as camel hair, mohair, horsehair, cattle hair, hogbristles, human hair; and additional keratins such as chicken feathers,turkey feathers, duck feathers, fur, animal hoofs, horn, synthetickeratin fibers, and so forth."

Moreparticularly this invention concerns the treatment of keratinousmaterials wherein the normal disulphide cross-linkages in the keratinmolecule are replaced by different and novel cross-linkages derived fromunsaturated sulphones, sulphoxides, or phosphine oxides whereby theproperties of the keratinous-material are altered in an advantageousdirection. The invention is concerned not only with the; processeswhereby such chemical alterations are produced but also with the novelmodified keratins produced by such chemical action. Further objects,features, and advantages of be evident from the following dc,-

wherein the Xs represent the polypeptide chains.

It is also known in the art that the disulphide linkages in a typicalkeratin fiber, such as wool, are the cause of certain disadvantageousproperties exhibited by the fiber. Thus the disulphide linkages arereadily attacked and disrupted by various agencies such as chemicalreagents (particularly lalkalis, oxidizing agents, reducing agents),ultra-violet light, insects, enzymes, microprganisms, and so forth. Whenthe disulphide bonds are disrupted the fiber is greatly weakened, thuswhen it is subjected .to tensile forces the individual polypeptidechains may be pulled apart since the disulphide bonds which normallyhold the polypeptide chains together are no longer present or at leastthe number of them is reduced.

Patented Get. 4, less It has been shown in the prior art that theproperties of keratins, particularly wool, can be enhanced by theprocess of alkylation. In this procedure, the wool is treated with areducing agent to disrupt the disulphide linkages thus converting the-SS bond into two thiol (-SH) bonds, one attached to each polypeptidechain. The wool is then reacted with an alkylating agent such as1,2-dibromoethane whereby the polypeptide chains are re-linked, thistime through a bond. It has also been shown that the reduction andalkylation can be performed essentially simultaneously by applying asolution containing both a reducing agent and the alkylating agent tothe wool.

In these known alkylating procedures the cross-linking reagent isinvariably an organic dihalide such as ethylene dichloride, ethylenedibromide, methylene dichloride, trimethylene dibromide, and so forth.The use of these reagents brings about several disadvantages. In thefirst place most of these .dihalides, particularly those of practicalimportance are volatile and toxic liquids. In using these reagentslosses occur by vaporization of the reagent and the iumes are dangerousfrom a standpoint of the health of the operators in the plant. Anotherpoint, is that the dihalides require the use of alkaline conditions forthe formation of the desired S-alkylene-S- linkages. it is evident thatthese reagents couple with the thiol (-SH) groups by the elimination ofa hydrohalic acid in accordance with the equation:

2X-SH+BrC H Br X-SCH;SX+2HBr Therefore to cause the reaction to go inthe desired direction a base must be present to combine with theeliminated hydrohalic acid to remove it from the field of action. Theuse of strongly alkaline conditions although expedient is actuallyundesirableas it is well known that alkaline reagents cause a weakeningof keratin fibers and causes them to melt and decrease in hand.

It has now been found that more advantageous results are attained whenthere is used as the cross-linking reagent compounds of an entirelydifferent character than those used heretofore. The cross-linkingreagents used in accordance with this invention are organic compoundswhich contain at least two olefinic unsaturated groups, these groupsbeing linked to a sulphone, sulphoxide, or phosphine oxide radical.Representatives examples of the cross-linking reagents within thepurview of this invention are given below by way of illustration and notlimitation:

A. UNSATURATED SULPHONES These compounds may be represented by theformula:

0 RC=C C=CR i. i l) i i wherein the Rs stand for hydrogen or organicradicals of the aliphatic, cycloaliphatic or aroma-tic types. A typicalexample of R as an aliphatic hydrocarbon radical is methyl; otherradicals in this area are ethyl, propyl, isopropyl, butyl', etc.Atypical example of R as an aromatic hydrocarbon radical is phenyl;other aromatic radicals are tolyl, xylyl, naphthyl, ethylphenyl,cumenyl, cyclohexylphenyl, etc. A typical example of R as acycloaliphatic radical is cyclohexyl; other radicals in this categoryare methylcyclohexyl, phenylcyclohexyl, etc. Other radicals which may beused for R in the above formula are benzyl, phenylethyl,cyclohexylmethyl, cyclohexylethyl, phenylcyclohexy-l, benzylphenyl, andso forth.

R need not necessarily be a hydrocarbon radical but may containsubstituent groups, for example, carboxyl COOH SOzH

e O ONH:

' 60M @NH-C O-R e (In the above formulas, R is hydrogen or a hydrocarbonradical.)

It is of course understood that the various Rs need not be identicalradicals. Thus some of the Rs may be hydrogem the others may bedifierent organic radicals. The invention thus includes sulphones whichhave an asymmetrical configuration as Well as those of a symmetricalconfiguration. s

Listed below are examples of individual compounds which come within theambit of the invention. 'The nomenclature used is based on fundamental'vinyl groups 'phone, bis(Z-phenylvinyl) attached to the sulphoneradical and the carbon atoms are numbered as follows:

For example, thecompound 1-methyl-2-butylvinyl-1-ethy1-2,2'-diphenylvinyl sulphone has the. formula:

o4Hr-'-o=o-so r-o=0(OtH5)i V H CH3; CgHs v 7 Examples of individualunsaturated sul phones Divinyl sulphone, l-methylvinyl-vinyl sulphone,l-ethylvinyl-vinyl sulphone, l-propylvinyl-vinyl sulphone,1-1sopropylvinyl-vinyl sulphone, l-butylvinyl-vinyl sulphone,

2-methylvinyl-viny1 sulphone, 2-ethylvinyl-vinyl sulphone, v

Z-propylvinyl-vinyl sulphone, 2-isopropylvinyl-vinyl sulphone,Z-butylvinyl-vinyl sulphone, 1,2-dimethylvinylvinyl sulphone,1,2-diethylvinyl vinyl sulphone, 1',2-dipropylvinyl-vinyl sulphone,1,2-diisopropylvinylavinyl sulphone, 1,2-dibutylvinylviny1 sulphone,2,2-dimethylvinylvinyl sulphone, 2,2-diethylvinyl-vinyl sulphone;2,2-dipropylvinyl-vinyl sulphone, 2,2-diisopropylvinyl-viny1 sulphone,2,2-dibutylvinyl-vinyl' sulphone, 1,2,2-trimethy1- vinyl-vinyl sulphone,1,2,2-triethy1vinyl-vinyl sulphone, 1,2,2-tripropylvinyl-vinyl sulphone,1,2,2-triisopropylvinyl-vinyl sulphone, I,2,2tributylvinylvinylsulphone, bis(l-methylvinyl) sulphone, bis(l-ethylvinyl) sulphone, bis(l-propylviny1) sulphone, bis(l -isopropylvinyl) sulphone,bis(l-butylvinyl) sulphone, bis(2- methylvinyl) sulphone,bis(2-ethylvinyl) sulphone, bis(Z-propylvinyl) sulphone,bis(2-isopropylvinyl) sulphone, bis(Z-butylvinyl) sulphone,bis(1,2-dimethylvinyl) sulphone, bis( 1,2-diethylvinyl) sulphone, bis(1,2-dipropylvinyl) sulphone, bis(l,2-diisopropylvinyl) sulphone, bis( 1,Z-dibutylvinyl) sulphone, bis(2 ,2-dimethylvinyl) sulph ne,bis(2,2diethylvinyl) sulphone, bis(2,2-dipropylvinyl) sulphone,bis(2,2-diisopropylvinyl) sulphone, bis- (2,2-dibutylvinyl) sulphone,bis(l,2,2-trimethylviny1) sulphone, bis(1,2,2-triethylvinyl) sulphone,bis( 1,2,2-tripropylvinyl) sulphone, bis(1,2,2-triisopropylvinyl)sulphone, bis(1,2,2-tributylvinyl) sulphone, l-methyl-Z-ethylvinyl-vinylsulphone, 1-methyl-2-propylvinyl-viny1 sulphone,1-methyl-2-isopropylvinyl-vinyl sulphone, 1- methyl-Z-butylvinyl-vinylsulphone, l-ethyl-Z-methylvinylvinyl sulphone,1-propyl-2-rnethylvinylavinyl sulphone, 1- isopropyl-Z-methylvinyl-vinylsulphone, l-butyl-2-methylvinyl-vinyl sulphone,1-methy1-2,Z-diethylvinyl-vinyl sulphone,1-propyl-2,Z-diethylvinyl-vinyl sulphone,l-isopropyl-LZ-diethylvinyl-vinyl sulphone,1-butyl-2,2-diethylvinyl-vinyl sulphone, bis( l-methyl-Z-ethylVinyl)sulphone, bis(l-methyl-2-propylvinyl) sulphone, bis(l-methyl-Z-isopropylvinyl) sulphone, bis(l-methyl-Z-butylvinyl)sulphone, bis(l-ethyl-Z-methylVinyl) sulphone, bis(l-propyl-Z-methylvinyl) sulphone, bis(l isopropyl-Z-methylvinyl) sulphone,'bis(l-butyl-Z-methylvinyl) sulphone, bis(lmethyl-2,2-diethylvinyl)sulphone," bis(l-methyl-2,2-dipropylvinyl) sulphone,bis(1-methyl-2,2-diisopropylvinyl) sulphone,bis(1-methyl-2,2-dibutylvinyl) sulphone, lmethylvinyl-2'-ethylvinylsulphone, 2-methylvinyl-2'- ethylvinyl sulphone,1,Z-dimethylvinyl-Z'-ethylvinyl sulphone, 2,2'-dimethylvinyl-2-ethylvinyl sulphone, 1,2,2-trimethylvinyl-2'-ethylvinylsulphone, l-phenylvinyl-vinyl sulphone, 2-phenylviny1-vinyl sulphone,1,2-diphenylvinylvinylsulphone, 2,2-diphenylvinyl-vinyl sulphone, 1,2,2-triphenylvinyl-vinyl sulphone, bis(l-phenylvinyl) sulsulphone,bis(l,2-diphenylvinyl) sulphone, bis(2,2-diphenylvinyl) sulphone, bis-(l,2,2-triphenylvinyl) sulphone, .2-phenylvinyl-2-ethylvinyl sulphone,2-phenylviny1-2"-cyclohexylvinylsulphone, 2 -.phenylvinyl-2-benzylvinylsulphone, 2-phenylvinyl-Z- ethoxyethylvinyl sulphone,2-phenylvinyl-2'-phenoxyethylvinyl sulphone, 2-cyclohexylvinyl-vinylsulphone, 2-cyclohexylvinyl-2'-ethylvinyl sulphone,2-cycIoheXylvinyl-2'- benzylvinyl sulphone,Z-cyclohexylvinyl-Z'-ethoxyethylvinyl sulphone,2-cyclohexylvinyl-2"-phenoxyethylvinyl B. UNSATURATED SULPHOXIDES Thesecompounds may be represented by the formula ll RO=(IJSC=(IJR wherein Rhas the meaning as above described and exemplified.

C. UNSATURATED PHOSPHINE OXIDES These compounds may be represented bythe formula 6 ret-rt R R RR R wherein R has the meaning as abovedescribed and exemplified and wherein R represents an organic radicalfor example methyl, ethyl, propyl isopropyl, butyl, phenyl, tolyl,benzyl, phenylethyl, cyclohexyl, methylcyclohexyl, phenoxyethyl,ethoxyethyl, hydroxyethyl, hydroxyphenyl, hydroxycyclohexyl, vinyl,methylvinyl, phenylvinyl, cyclohexylvinyl, benzylvinyl, and so forth.

The cross-linking reagents of this invention react by an addition of thethiol groups of the reduced protein molecule to the unsaturated (vinyl)groups of the crosslinking agent. These unsaturated groups areactivated,

' and hence highly reactive, because of their adjacency to the sulphone,sulphoxide, or phosphine oxide group. The following equation illustratesthe type of reaction involved In the above equation, X represents thepolypeptide chain of the protein molecule.

It is evident from the above equation that the bridging or cross-linkingof the peptide moieties occurs by addition of the constituents of thethiol (SH) groups to the activated, olefinic double bonds of the divinylsulphone. A similar type of reaction will take place with the othercross-linking agents contemplated by this invention. It is evident thatwhere the cross-linking agent has three olefinic groups (trivinylphosphine oxide, for instance) the agent will take up three -SX groups.

In some instances, cross-linking may additionally occur through reactionof free aminogroups, hydroxyl groups, or amide groupsin the proteinmolecule with the unsaturated groups of the cross-linking agent. Suchreaction is illustrated by the following equation:

In the above equation, X represents the polypeptide chain of the proteinmolecule. By cross-linking the peptide chains of keratin fibers with thenovel agents fibers .which have marked advantages over. the natural ororiginal fiber. Thus the modified fiber has an increased resistance toshrinkage and felting when subjected to laundering or other procedureswherein the fiber is contacted with aqueous, especially aqueous-alkalinefluids. The modified fiber is increased in resistance to biologicaldegradation as by insects, bacteria, molds, and enzymes. The modifiedfiber has increased stability toward other potentially deleteriousagencies as for example sunlight, ultra-violet light, reagents such asalkalis, acids, reducing agents, and oxidizing agents used in dyeing andother textile-treating procedures. It is obvious that to attain amaximum stabilizing efiect on the fiber, a considerable proportion,i.e., over 25% of the disulphide linkages present in the original ornatural fiber should be replaced by the sulphone, sulphoxide, orphosphine oxide crosslinkages. Where partial modification isdesired theconditions of reaction, for example, the temperature, concentration ofreagents, time of reaction, etc., may be varied as desired to attain anydegree of replacement of disulphide linkages by the describedcross-linkages. Thus by such variation of reaction conditions, theuptake of sulphone (or sulphoxide or phosphine oxide) by the fibers maybe varied, for example, from about 1% to about 25%, with correspondingvariation in the properties of the modified fibers. The properties ofthe modified fiber will also depend to a lesser extent on the type ofcompound chosen as the cross-linking agent. Whether or not anyparticular cross-linking agent is suitable for the desired type ofmodification of the original fiber can be determined by conducting apilot reaction with the selected cross-linking agent and noting thecharacteristics of the modified fiber by conducting conventional teststhereon.

The treatment of the fiber or other keratinous material to replace thedisulphide bonds by the novel sulphone, sulp-hoxide or phosphine oxidelinkages is preferably carried out in what may be termed a two-stepprocess. This procedure involves two separate phases as follows: First,the keratin is treated with a reducing agent in known manner to spliteach disulphide bond into thiol radicals or other radicals which behavein subsequent reaction similar to thiol radicals. The reduced keratin isthen reacted with the cross-linking agent to establish the new bondsbetween the polypeptide chains.

Regarding the two-step process briefly noted above, the keratin is firstreacted with a reducing agent. As this agent one may use varioussulphur-containing, reductive, disulphide-splitting agents such assodium sulphide, sodium sulphite, sodium bisulphite, other water-solublesalts of sulphurous or hydrosulphuric acid, or preferably organiccompounds containing thiol groups. Examples of the latter arethioglycolic acid, sodium thioglycolate, beta-mercapto ethanol,1,2-dithioglycerol, 'butyl mercaptan, and so forth. In general thereduction is carried out by immersing the keratin material in watercontaining an amount of the reducing agent in excess of thatstoichiometrically calculated to reduce all the disulphide linkages inthe amount of keratin material used. Where the reducing agent haslimited solubility in water, a wetting and dispersing agent such as along chain alkyl benzene sulphonate or long chain alkyl sodium sulphatemay be added to keep the reducing agent in suspension and to promotebetter contact between the keratin and the reducing agent. Suchconditions as temperature and time of reaction may be varied dependingon such factors as the type of keratin being treated, the eificacy ofthe reducing agent chosen, the degree of splitting of disulphide bondsdesired and so forth. In general the temperature may vary from about 20C. to about C. Where the keratin material is a fiber such as wool or furor hair, itis preferred to limit the upper range of temperature to about60 C. thus to avoid degradation polypeptide chains or other undesirableside-reactions. Where refractory 'keratins such as cattle hoof or hornare being treated,

higher temperatures such as available in conducting the process undersuperatrnospheric pressure, maybe necessary to obtain the desiredreduction of disulphide bonds. The reaction is discontinued when thedesired proportion of disulphide bonds has been split. It is to be notedthat splitting of the disulphide bonds results in a drastic weakening ofthefiber so that the extent of the reduction can easily be followed byconducting tensile strength measurements from time to time on the fiberundergoing reaction. In general the time of reaction may vary from 30minutes to 24 hours or more depending on the nature of the keratinmaterial, the temperature of reaction, the eflicacy of the reducingagent, etc. The medium in the reduction may contain an alkaline agentsuch as sodium hydroxide, potassium hydroxide, sodium carbonate, borax,or the like to promote the splitting reaction. Wherealkaline material isused the pH of the medium should be below about pH 9 to avoid splittingof polypeptide chains. Generally it is preferred to use slightly acid orneutral conditions (about pH 7) to avoid any possibility of peptidedegradation.

After the reduction step has been completed, the reduced keratinmaterial is thoroughly washed to remove all excess reducing agent.Agents such as organic thiols if left in the keratin mass would reactwith the crosslinking agent applied in the next step. Solvents such asalcohol, acetone, benzene, etc. may be used as necessary to removeresidual reducing agent.

The washed, reduced keratin is then immersed in a solution of thecross-linking agent in an amount of one-half moi of the agent for eachthiol groupin the reduced kera- Usually,-an excess of the cross-linkingagent is used to ensure complete reaction. Where the cross-linking agentis soluble in water, water may be used as a solvent for thecross-linking agent. In other'cases it may be necessary to use an inertsolvent in which the agent is soluble,.for example, ethanol, propanol,butanol, benzene, dioxane, ether, petroleum ether, gasoline, hexane,etc. Where water is used as the medium, the cross-linking agent may bedispersed in the aqueous medium by the use of a wetting and dispersingagent such as a long chain alkylbenzene sodium sulphonate, long chainalkyl sodium sulphate, or the like. The temperature of the reaction maybe varied from about to 100 C. Where the material being processed is afiber such as wool, hair, fur, etc. it is preferred to use a temperatureno higher thanabout 60 C.-whereby to avoid degradation of thepolypeptide chains. The time of reaction will vary depending onthetemperature of reaction, the reactivity of the cross-linking agentselected and the degree of modification desired. In general the reactionmay take anywhere from 30 minutes to 24 hours or more. In most caseswith cross-linking agents wherein all or most of the Rs are hydrogen thecreation of the new cross links will proceed more rapidly than where theagents have many organic substituents on the vinyl groups. The extent ofthe cross-linking reaction can be followed by conducting tensilestrength or similar physical tests on the fiber from time to timesincethe establishment of the cross links between polypeptide chainswill result keratin materials in which at lease some of the di-sulphidelinkages of the keratin molecule have been disrupted and replaced bylinkages of the type represented by where X represents the portion ofthe keratin molecule to which the disrupted disulphide linkage is.attached, It is an integer from 2 to 3, and M represents a compoundoriginally containing two to three olefinic unsaturated groups, each ofsaid groups being directly linked to a radical selected from the classconsisting of the sulphone, sulphoxide, and phosphine oxide radicals,and wherein in the chemically modified keratin, the olefinic groups aresatisfied by addition of an -SX and, a H radical per olefinic group.

The products of the invention, wherein the keratin is converted tolinkages of the type represented by XS SX wherein the Xs representportions of the wool molecule to which the disrupted disulpln'delinkages are attached and M represents a compound originally containingtwo olefinic unsaturated groups, each of said groups being directlyattached to a sulphone radical, and wherein in the chemically modifiedwool, the olefinic groups are satisfied by addition of an SX and a Hradical per olefinic group.

The invention is further demonstrated by the following example:

A lot of 8 /2 oz. white flannel wool cloth was thorough ly cleaned bysuccessive extraction with ether, alcohol, and water. The extracted woolwas dried and cut into squares of approximately 2 grams dry weight.

The wool samples were then reduced by soaking them for one hour at 50 C.in a 0.35 M solution of Z-mercaptoethanol in water, using 30 ml. pergram of wool. The reduced cloth samples were then washed thoroughly inrunning water. 7

The reduced Wool was then immersed in a solution of divinyl sulphone in0.1 M sodium borate buffer solution using 50 ml. per gram of wool... Theconcentration of the sulphone was 2 millimoles in 50 ml. of the aqueousbuffer. After agitating the wool in the sulphone solution for' 30minutes at room temperature, the wool was washed in running water anddried.

The treated wool and samples of the original wool were subjected tovarious tests described below as a measure of the effectiveness of thechemical modification.

Alkali solubility, determined by immersing the wool in 0.1 N sodiumhydroxide for one hour at 65 C. according to the method of Harris'andSmith (American Dyestuif Reporter, vol. 25, p. 542, 1936). The 'loss inweight was determined after thorough washing with water.

Solubility in ammonia after treatment with peracet-ic acid-carried outaccording to Alexander et a1 (Biochem. Journal, vol. 52, p. 177, 1952).Samples of the flannel weighing near 0.5 gram were" immersed in ml. of1.6% peracetic acid for 25 hours. After washing the samples were treatedfor 24 hours with 100 ml. of 0.3 M ammonia. The loss in weight wasdetermined after thorough washing with water. 0

Degree of supercontraction+determined by measuring the length of thefiber before and after being immersed in 5% sodium bisulphite at 100C.for 1 hour. The supercontraction is the percentage proportion of (a) thedecrease in length after treatment with the sodium bisulphite to (b) theoriginal length of the fiber. This property of the wool is an index ofcross-linking of the protein molecule; the less the contraction aftertreatment with bisulphite', the greater is the degree of crosslinkinglfThe results obtained are tabulated below:

Having thus described the invention, what is claimed is:

1. A method of chemically modifying a keratin which comprises reducingthe keratin by reacting it with a sulphurcontaining, reductive,disulphide-splitting agent capable of converting the S-S bond of thekeratin into two thiol (-SI-I) groups, at a pH of about to 7, thenreacting the reduced keratin at a temperature about from 20 to 100 C.with a compound containing two to three olefinic unsaturated groups,each of said groups being directly linked to a radical selected from theclass consisting of the sulphone, sulphoxide, and phosphine oxideradicals.

2. A method of chemically modifying wool which comprises reducing woolby reacting it with a sulphur-containing, reductive,disulphide-splitting agent capable of converting the --S-S bond of thewool into two thiol (-SH) groups, at a pH of about 5 to 7, then reacting10 the reduced wool at a temperature about from 20 to C. with a sulphoneof the formula:

rrre R R R R wherein the Rs represent radicals of the class consistingof hydrogen and hydrocarbon radicals.

3. The process of claim 2 wherein the sulphone is divinyl sulphone.

Alexander et al.: Wool, Its Chemistry and Physics," Reinhold Pub. Corp,N.Y., 1954, p. 254.

'Olcott et al.: Chemical Reviews, August 1947, p. 187.

Grant et al.: Jour. of Biol. Chem. pp. 485-493, pub. June 28, 1946.

1. METHOD OF CHEMICALLY MODIFYING A KERATIN WHICH COMPRISES REDUCING THEKERATIN BY REACTING IT WITH A SULPHUR-CONTAINING, REDUCTIVE,DISULPHIDE-SPLITTING AGENT CAPABLE OF CONVERTING THE -S-S- BOND OF THEKERATIN INTO TWO THIOL (-SH) GROUPS, AT A PH OF ABOUT 5 TO 7, THENREACTING THE REDUCED KERATIN AT A TEMPERATURE ABOUT FROM 20 TO 100* C.WITH A COMPOUND CONTAINING TWO TO THREE OLEFINIC UNSATURATED GROUPS,EACH OF SAID GROUPS BEING DIRECTLY LINKED TO A RADICAL SELECTED FROM THECLASS CONSISTING OF THE SULPHONE, SULPHOXIDE, AND PHOSPHINE OXIDERADICALS.